Gate tie-down enablement with inner spacer

ABSTRACT

A gate tie-down structure includes a gate structure including a gate conductor and gate spacers and inner spacers formed on the gate spacers. Trench contacts are formed on sides of the gate structure. An interlevel dielectric (ILD) has a thickness formed over the gate structure. A horizontal connection is formed within the thickness of the ILD over an active area connecting the gate conductor and one of the trench contacts over one of the inner spacers.

BACKGROUND Technical Field

The present invention relates to semiconductor processing, and moreparticularly to a gate tie-down structure that permits gate contacts inactive areas and self-aligns these gate contacts with source/draincontacts.

Description of the Related Art

In conventional complementary metal oxide semiconductor (CMOS)processing, gate contacts are formed over shallow trench isolation (STI)regions. Gate contacts connect a gate line to upper metal layers indevice designs. In many instances, providing the gate contacts in STIregions can result is a large amount of chip area being lost.

Gate tie-down structures or regions provide a connection between thegate contact and a source/drain (S/D) region contact. The formation of agate tie-down structure may result in shorts between a silicide regionof the S/D region or with conductive material of an adjacent gate. Thisis due in part to the small margins of dielectric materials betweenthese structures and the close proximity of the conductive bodies.

SUMMARY

A gate tie-down structure includes a gate structure including a gateconductor and gate spacers and inner spacers formed on the gate spacers.Trench contacts are formed on sides of the gate structure. An interleveldielectric (ILD) has a thickness formed over the gate structure. Ahorizontal connection is formed within the thickness of the ILD over anactive area connecting the gate conductor and one of the trench contactsover one of the inner spacers.

A method for forming a gate tie-down includes opening up a cap layer andrecessing gate spacers on a gate structure to expose a gate conductor;forming inner spacers on the gate spacers; etching contact openingsadjacent to sides of the gate structure down to a substrate below thegate structures; and forming trench contacts on sides of the gatestructure. An interlevel dielectric (ILD) is deposited on the gateconductor and the trench contacts and over the gate structure. The ILDis opened up to expose the trench contact on one side of the gatestructure and the gate conductor. A second conductive material is formedto provide a self-aligned contact down to the trench contact on the oneside of the gate structure and to form a gate contact down to the gateconductor and to form a horizontal connection within the ILD over anactive area between the gate conductor and the self-aligned contact.

Another method for forming a gate tie-down includes opening up a caplayer and recessing gate spacers on a gate structure to expose a gateconductor; forming inner spacers on the gate spacers; etching contactopenings adjacent to sides of the gate structure down to a substratebelow the gate structure; filling the contact openings with a firstconductive material; recessing the first conductive material and thegate conductor below the inner spacers to form trench contacts on sidesof the gate structure; depositing an interlevel dielectric (ILD) on thegate conductor and the trench contacts and over other gate structures;opening up the ILD to expose the trench contact on one side of the gatestructure and the gate conductor; forming a second conductive materialto form a self-aligned contact down to the trench contact on the oneside of the gate structure and to form a gate contact down to the gateconductor; and planarizing the second conductive material and the ILD toform a horizontal connection within the ILD over an active area betweenthe gate conductor and the self-aligned contact.

A gate tie-down structure includes a gate structure including a gateconductor and gate spacers, inner spacers formed on the gate spacers andtrench contacts formed on sides of the gate structure. A firstinterlevel dielectric (ILD) is configured to bury the gate structure,and a second interlevel dielectric (ILD) is formed on the first ILD, thesecond ILD having a thickness. A self-aligned contact connects to thetrench contact on one side of the gate structure. A gate contact isconnected to the gate conductor. A horizontal connection is formedwithin the thickness of the second ILD over an active area and connectsthe gate conductor and the self-aligned contact over one of the innerspacers.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 is a cross-sectional view of a semiconductor device having gatestructures formed in an interlevel dielectric (ILD) in accordance withthe present principles;

FIG. 2 is a cross-sectional view of the semiconductor device of FIG. 1having gate structures recessed to expose a gate conductor in accordancewith the present principles;

FIG. 3 is a cross-sectional view of the semiconductor device of FIG. 2showing a spacer layer formed in accordance with the present principles;

FIG. 4 is a cross-sectional view of the semiconductor device of FIG. 3showing spacers formed on gate spacers in accordance with the presentprinciples;

FIG. 5 is a cross-sectional view of the semiconductor device of FIG. 4showing trench contact holes etched adjacent to the gate spacers inaccordance with the present principles;

FIG. 6 is a cross-sectional view of the semiconductor device of FIG. 5showing the trench contact holes filled with conductive material inaccordance with the present principles;

FIG. 7 is a cross-sectional view of the semiconductor device of FIG. 6showing the conductive material planarized in accordance with thepresent principles;

FIG. 8 is a cross-sectional view of the semiconductor device of FIG. 7showing the conductive material recessed to below the inner spacers inaccordance with the present principles;

FIG. 9 is a cross-sectional view of the semiconductor device of FIG. 8showing another ILD formed in recessed regions below the inner spacersin accordance with the present principles;

FIG. 10 is a cross-sectional view of the semiconductor device of FIG. 9showing the ILD etched to expose one trench contact and the gateconductor below the inner spacers in accordance with the presentprinciples;

FIG. 11 is a cross-sectional view of the semiconductor device of FIG. 10showing a conductive material deposition, and the conductive materialand the ILD planarized to form a gate tie-down structure with a gatecontact, a connection (in the ILD) and self-aligned contact inaccordance with the present principles; and

FIG. 12 is a block/flow diagram showing methods for forming a gatetie-down in accordance with the present principles.

DETAILED DESCRIPTION

In accordance with the present principles, a gate tie-down structure andmethods for fabrication are provided. The gate tie-down provides a gatecontact (CB) that is able to short against a self-aligned contact (CA)without shorting against a trench silicide (TS) contact. The gatecontact provides a connection to a gate conductor (PC) of a gatestructure employed in a transistor device. The gate conductor, in someinstances, may be connected to a source or drain region. This isreferred to as a gate tie-down. Gate tie-downs in accordance with thepresent principles may be provided over active regions without sufferingfrom the shorting issues of conventional structures. In addition, thegate tie-downs include a gate contact that is self-aligned to asource/drain contact. The tie-down structure provides a gate contactthat can “fly” over the source drain contact making the design morecompact and saving precious chip area. For example, the gate tie-downstructure can be allowed on or over active areas (AA). The gate contactstructure enables the gate contact to fly over a source/drain contact toreduce a layout footprint. The gate tie-down structure may be employedin memory devices, e.g., static random access memory (SRAM), processors,or other chip devices.

It is to be understood that the present invention will be described interms of a given illustrative architecture; however, otherarchitectures, structures, substrate materials and process features andsteps may be varied within the scope of the present invention.

It will also be understood that when an element such as a layer, regionor substrate is referred to as being “on” or “over” another element, itcan be directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

The present embodiments may be included in an integrated circuit orintegrated circuit design. A design for an integrated circuit chip maybe created in a graphical computer programming language, and stored in acomputer storage medium (such as a disk, tape, physical hard drive, orvirtual hard drive such as in a storage access network). If the designerdoes not fabricate chips or the photolithographic masks used tofabricate chips, the designer may transmit the resulting design byphysical means (e.g., by providing a copy of the storage medium storingthe design) or electronically (e.g., through the Internet) to suchentities, directly or indirectly. The stored design is then convertedinto the appropriate format (e.g., GDSII) for the fabrication ofphotolithographic masks, which typically include multiple copies of thechip design in question that are to be formed on a wafer. Thephotolithographic masks are utilized to define areas of the wafer(and/or the layers thereon) to be etched or otherwise processed.

Methods as described herein may be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

Reference in the specification to “one embodiment” or “an embodiment” ofthe present principles, as well as other variations thereof, means thata particular feature, structure, characteristic, and so forth describedin connection with the embodiment is included in at least one embodimentof the present principles. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment”, as well any other variations,appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This may be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, a cross-sectional view of apartially fabricated semiconductor device 10 is shown in accordance withthe present principles. The device 10 is formed on a substrate 12, whichmay include any suitable substrate materials, such as Si, SiGe, SiC,III-V materials, etc. Gate structures 18 are formed on the substrate 12and may include source/drain (S/D) regions 26 adjacent to the gatesstructures 18. The gate structures 18 may include a gate dielectric 28(e.g., an oxide) and a gate conductor 22, which may include a metal,doped polysilicon or other suitable gate conductor material. Spacers 20are formed on sidewalls of the gate conductor 22 and a cap layer 24 isformed over the gate conductor 22. The spacers 20 and the cap 24 mayinclude a silicon nitride material, although other dielectric materialsmay be employed. Gate structures 18 are buried in an interleveldielectric (ILD) material 14, such as an oxide. Another ILD 16 is formedover the gate structures 18 and on the first ILD 14. The ILD 16 may alsoinclude an oxide.

Referring to FIG. 2, recesses 30 are etched through the ILD 14 and ILD16. The cap layer 24 is removed, and the spacers 20 are recessed toexpose the gate conductors 22 for selected gate structures 18. Therecesses 30 are formed to gain access to the gate conductors 22 to dropin a gate contact for connecting the gate conductor to upper level metalstructures to provide gate control. The recesses 30 are formed byperforming a lithographic patterning process followed by an etch processto open the recesses 30 and expose the gate conductors 22. The etchprocess may include a reactive ion etch (RIE). The recesses 30 allow fora self-aligned contact to be provided as will be described.

Referring to FIG. 3, a spacer dielectric layer 32 is conformally formedon the ILD 16 and in the recesses 30 on sidewalls, and over the spacers20 and the gate conductors 22. The spacer dielectric layer 32 mayinclude silicon nitride although other materials may be employed, e.g.,high-k dielectrics or other high selective etch stop layer (ESL)materials.

Referring to FIG. 4, a directional etch process may be performed toremove the spacer dielectric layer 32 from horizontal surfaces. Thedirectional etch process may include RIE, e.g., employing an etchchemistry including BCl₃. The removal of the spacer dielectric layer 32from the horizontal surfaces forms inner spacers 34.

Referring to FIG. 5, a lithographic patterning process is employed toform a mask for etching the ILD 16 and ILD 14. A RIE is performed toexpose S/D regions 26 adjacent to the gate structure 18, which isselected for the formation of a gate tie-down structure. The RIE formstrenches 36. The etch exposes the S/D regions 26 to enable a trenchsilicide (TS) to be formed. The silicide may be formed on the S/Dregions 26 by depositing a metal and annealing to cause a mixing of themetal with material of the S/D regions 26 (to form a silicide).

Referring to FIG. 6, a deposition process is performed to fill trenches30 between inner spacers 34 and to fill trenches 36 adjacent to the gatestructures 18 with a conductive material 38. The deposition process mayinclude a chemical vapor deposition (CVD) process although otherdeposition processes may be employed. The conductive material 38 mayinclude W, although other metals may be employed, e.g., Al, Cu, Ag, etc.The conductive material 38 connects with the exposed gate conductors 22as well as the S/D regions 26. The conductive material 38 preferablyincludes the same materials as the gate conductors 22.

Referring to FIG. 7, a planarization process is performed to planarize atop surface of the device 10 to remove excess conductive material 38.The planarization process may include a chemical mechanical polish (CMP)process.

Referring to FIG. 8, a recess process is performed to recess theconductive material 38 below the inner spacers 34. The recess processmay include a RIE process that selectively removes the conductivematerial 38 relative to the ILD 14, the spacers 20 and the inner spacers34. In one embodiment, the ILD 16 includes oxide, and the spacers 20 and34 include nitride. Recessing the conductive material 38 forms trenchsilicide (TS) contacts 40, which contact the S/D regions 26. Theplanarization process may include a chemical mechanical polish (CMP)process.

Referring to FIG. 9, another ILD 42 is deposited on the device 10. TheILD 42 may include an oxide although other dielectric materials may beemployed. The ILD 42 fills down to the TS contacts 40 and the gateconductors 22. An ILD planarization process (e.g., CMP) may be performedto planarize the ILD 42 on a top surface of the device. Theplanarization process may not be needed.

Referring to FIG. 10, an open process is employed to open up a gatetie-down structure. Etching processes are employed to remove the ILD 42in areas defined by lithographic techniques. Regions 48 are opened up byremoving the ILD 42 between the inner spacers 34 and spacers 20 toexpose the gate conductor 22. Regions 50 are opened up by removing theILD 42 to expose a TS contact 40. Other TS contacts 40 may be opened upat different locations along a line of the gate structures 18.

In one embodiment, the etching process to remove ILD 42 includes alithography, etch, lithography, etch (LELE) process. This may include aself-aligned contact (CA) lithography followed by an etch to open upregion 44 over region 50. Then, a self-aligned gate contact (CB)lithography is performed followed by an etch to open up region 44 overregion 48. The etching processes preferably include RIE, although otheretching techniques may be employed.

In another embodiment, a lithography, freeze, lithography, etch (LFLE)process may be employed. First, a CA lithography is performed to patternthe ILD 42 for a contact in region 50, but before etching a first resistmaterial is chemically frozen and a second lithography process isperformed by depositing a second resist. The second resist is foretching the regions 48 for the gate contacts (CB). Then, an etch isperformed to remove the ILD 42 as shown in FIG. 10 in accordance withboth the first and second resist patterns. The etching processpreferably includes RIE, although other etching techniques may beemployed.

In another embodiment, an extreme ultraviolet (EUV) lithography processmay be employed where a same color lithography is performed for both theCA and CB patterning. The etch mask is formed and then etched toconcurrently form the CA and CB contacts openings in regions 48 and 50,respectively. The etching process preferably includes RIE, althoughother etching techniques may be employed.

The etching processes described (e.g., LELE, LFLE and EUV) are allperformed with a high selectivity between material ILD 42 (e.g., oxide)and the material of spacers 22 and inner spacers 34 (e.g., nitride).

Referring to FIG. 11, a deposition process is performed to deposit aconductive material 60 to form gate contacts 54 (CB), contacts 56 (CA),and a gate tie-down structure 52. The conductive material 60 preferablyincludes a same material as employed for TS contacts 40 and gateconductor 22. In one embodiment, the conductive material 60 includes W,although other metals may be employed. The conductive material 60 isplanarized to recess the material 60 such that a portion of theconductive material 60 forms a connection between the gate contact 54and the contact 56 (that connects to the TS contact 40).

In accordance with the present principles, the gate tie-down structure52 provides a self-aligned gate contact 54 that shorts directly tocontact 56 (S/D contact) and not directly to the TS contact 40. Thespacers 20 and inner spacer 34 provide a dielectric barrier thatprevents direct shorting between the gate contact 54 and the TS contact40. In addition, the gate contact 54 is self-aligned with the S/Dcontact 56. The gate contact 54 is made within the active region (overS/D regions 26). This reduces the layout footprint of the device 10. Inother words, a horizontal connection 58 is made over the inner spacers34 directly between the gate contact 54 and the self-aligned contact 56using vertical space provided by the ILD 42. This connection 58 is madewithout having to use layout area, which would normally be consumed byplacing the connections over an STI region outside of the S/D regions(active area). The present principles may be implemented in 7 nmtechnology, although other technology sizes (larger or smaller) maybenefit from the present principles.

Referring to FIG. 12, methods for forming a gate tie-down are shown inaccordance with the present principles. In some alternativeimplementations, the functions noted in the blocks may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

In block 102, after gate structures and source and drain (S/D) regionsare formed, a cap layer may be opened up and gate spacers recessed on agate structure to expose a gate conductor. This is performed byemploying a lithographic patterning process and etch, e.g., by RIE. Inblock 104, inner spacers are formed on the gate spacers. This mayinclude depositing a spacer layer (e.g., nitride) followed by a spaceretch (e.g., RIE). In block 106, contact openings are etched adjacent tosides of the gate structure down to a substrate below the gatestructures. These openings expose the S/D regions for the formation oftrench contacts (TS). In block 108, the contact openings are filled witha first conductive material. In block 110, the first conductive materialand the gate conductor are recessed below the inner spacers to formtrench contacts on sides of the gate structure. In block 112, aninterlevel dielectric (ILD) is deposited on the gate conductor and thetrench contacts and over the gate structure (e.g., on an ILD whichburies the gate structures up to the cap layer).

In block 114, the ILD is opened up to expose the trench contact on oneside of the gate structure and the gate conductor. In block 116, openingup the ILD may include performing a lithography, etch, lithography, etch(LELE) procedure wherein one lithography and etch forms a contact holefor the self-aligned contact and the other lithography and etch forms acontact hole for the gate contact. In block 118, opening up the ILD mayinclude performing a lithography, freeze, lithography, etch (LFLE)procedure wherein one lithography forms a contact hole pattern for theself-aligned contact, which is frozen, and the other lithography forms acontact hole pattern for the gate contact before etching with bothpatterns. In block 120, opening up the ILD may include performing anextreme ultraviolet (EUV) lithography using a same color lithography toform patterns for the gate contact and the self-aligned contact beforeetching.

In block 122, a second conductive material is formed to provide aself-aligned contact down to the trench contact on the one side of thegate structure and to form a gate contact down to the gate conductor. Inblock 124, the second conductive material and the ILD are planarized toform a horizontal connection within the ILD over an active area betweenthe gate conductor and the self-aligned contact. The ILD includes athickness above a cap layer of gate structures and the horizontalconnection is formed within the ILD thickness. The gate spacers and theinner spacers permit contact between the self-aligned contact and thegate contact and prevent contact between the trench contact and the gateconductor. The gate contact is self-aligned to the trench contact. Inblock 126, processing continues to complete the device.

Having described preferred embodiments for gate tie-down enablement withan inner spacer (which are intended to be illustrative and notlimiting), it is noted that modifications and variations can be made bypersons skilled in the art in light of the above teachings. It istherefore to be understood that changes may be made in the particularembodiments disclosed which are within the scope of the invention asoutlined by the appended claims. Having thus described aspects of theinvention, with the details and particularity required by the patentlaws, what is claimed and desired protected by Letters Patent is setforth in the appended claims.

1. A gate tie-down structure, comprising: inner spacers formed on gatespacers of a gate structure; an interlevel dielectric (ILD) formed overthe gate structure and over a region adjacent to the gate structure; anda connection formed within the ILD over an active area connecting a gateconductor and at least one of multiple trench contacts over at least oneof the inner spacers.
 2. The structure as recited in claim 1, whereinthe gate spacers and the inner spacers permit contact between aself-aligned contact formed adjacent to one of the gate spacers and agate contact, which contacts the gate conductor.
 3. The structure asrecited in claim 2, wherein the gate spacers and the inner spacersprevent contact between another one of the multiple trench contacts andthe gate conductor.
 4. The structure as recited in claim 2, wherein thegate contact is self-aligned with the at least one of multiple trenchcontacts.
 5. The structure as recited in claim 2, wherein theself-aligned contact includes a second conductive material.
 6. Thestructure as recited in claim 1, wherein the structure is formed in theactive area to reduce device area.
 7. The structure as recited in claim1, wherein the inner spacers are formed on the gate spacers.
 8. Thestructure as recited in claim 1, wherein the structure is included in astatic random access memory.
 9. The structure as recited in claim 1,wherein the ILD includes a thickness above a cap layer of the gatestructure.
 10. The structure as recited in claim 9, wherein the caplayer includes a silicon nitride material.
 11. A gate tie-downstructure, comprising: inner spacers formed on gate spacers of a gatestructure; and a connection, formed in an interlevel dielectric (ILD)thickness above a cap layer of the gate structure, connecting between acontact on one side of the gate structure and a gate conductor over anactive area and over one of the inner spacers.
 12. The structure asrecited in claim 11, wherein the gate spacers and the inner spacersprevent contact of the gate conductor to a second contact on the otherside of the gate structure.
 13. The structure as recited in claim 11,wherein the contact includes a trench contact connected to a gatecontact and the gate contact is self-aligned with the trench contact.14. The structure as recited in claim 11, wherein the structure isformed in the active area to reduce device area.
 15. The structure asrecited in claim 11, wherein the inner spacers are formed on the gatespacers.
 16. The structure as recited in claim 11, wherein the contactincludes a same material as the gate conductor.
 17. The structure asrecited in claim 11, wherein the structure is included in a staticrandom access memory.
 18. The structure as recited in claim 11, whereinthe gate spacers and the inner spacers permit contact between aself-aligned contact and the contact and prevent contact between thetrench contact and the gate conductor.
 19. The structure as recited inclaim 11, wherein the ILD is above a cap layer of the gate structure.20. The structure as recited in claim 18, wherein the inner spacers arebelow the thickness of the ILD.